With the help of this guide you can measure several temperatures (wired, in air, water and even in the ground). The data is transmitted via WiFi to your smartphone (Android and iOS) and helps you to monitor e.g. your hot water tank, your garden house and much more. This project uses a NodeMCU Amica v2 (based on the ESP8266 microcontroller) and two wired DS18B20 sensors. The current measurement data is also shown on the OLED display.